1. Technical Field
The present invention relates to a dielectric composition, and more particularly, to a dielectric composition usable in a microwave band.
2. Description of the Related Art
A frequency used in communication components has been currently expanded to a microwave band due to development in technology in an information and communication field such as mobile communication and satellite broadcasting. The microwave refers to an electromagnetic wave in the frequency range of 300 MHz to 300 GHz, and an expansion to the microwave band is inevitably required in order to overcome a limitation in a usage frequency and allow larger demands as kinds and amounts of information become increased.
In order to achieve elements such as a duplexer, an LC filter, and the like, in the microwave band, since concept of a distributed circuit utilizing a λ/4 length is used, a dielectric composition having a dielectric constant of 15 to 100 and a high quality coefficient is needed. Examples of the representative dielectric composition include ZrO2—SnO2—TiO2 and BaO—TiO2 compositions having a dielectric constant of 40, and the dielectric compositions are used as the LC filter, or the like by applying a low temperature co-fired ceramic (LTCC) technology thereto.
The LTCC technology, which is a technology in which a dielectric ceramic is fired at a temperature of 950° C. or less by adding a low temperature sintering agent thereto, has an advantage in that Ag or Cu having excellent electric conductivity is usable as internal electrodes, and has the ultimate goal of three dimensional complex module having various passive components embedded therein.
A low temperature sintering oxide such as B2O3 or CuO has been mainly applied to the dielectric composition such as BaO—Bi2O3—Nd2O3—TiO2, BaTi4O9, Ba2Ti4O20, (Mg, Ca)TiO2, or (Zr, Sn)TiO4, having a temperature coefficient of resonant frequency of a value near 0 ppm/° C.
In particular, U.S. Pat. No. 5,872,071 discloses that BaCuO2—CuO, the low temperature sintering agent, is added to a (Zr, Sn)TiO4 composition having a dielectric constant of 40 in a range of 0.1 to 50 wt % to decrease a sintering temperature to be 1000° C. or less, wherein the dielectric constant is 35 to 40 and a quality coefficient (Q×f) is 7,000 to 35,000 GHz.
However, when reviewing the existing microwave dielectric compositions, the dielectric compositions having the dielectric constant of 50 or more, and in particular, 70 or more are rare, a BaO—Bi2O3—Nd2O3—TiO2 composition or a BaO—PbO—Nd2O3—TiO2 composition has been developed as a representative composition having the dielectric constant of 70 or more; however, has a problem in that PbO or Bi2O3 which is environmentally harmful is applied thereto.